LEIPZIG, Germany — Megalodon – the biggest shark that ever lived – likely met its extinction at the hands (or fins) of the great white shark, according to new research.
An international team says the huge and powerful sea monster likely lost the battle for resources to its smaller and nimbler rival. A study of fossilized teeth shows they chased the same animals, including whales, dolphins, and porpoises.
“These results likely imply at least some overlap in prey hunted by both shark species,” says co-author Professor Kenshu Shimada of DePaul University in a media release.
Analysis of zinc levels found they were at the top of the food chain, meaning nothing ate them. The team generated a database of values across 20 living and prehistoric shark species, ranging from aquarium and wild individuals to the megalodon.
“Our results show, that both megalodon and its ancestor were indeed apex predators, feeding high up their respective food chains,” says co-author Prof. Michael Griffiths from William Paterson University. “But what was truly remarkable is that zinc isotope values from Early Pliocene shark teeth from North Carolina, suggest largely overlapping trophic levels of early great white sharks with the much larger megalodon.”
Megalodon towered over modern sharks
Scientists believe megalodon was three-and-a-half times bigger than the great white — reaching 65 feet in length and weighing more than 50 tons. Its serrated seven-inch teeth and vertebrae are all that remain now. A shark’s skeleton consists largely of cartilage, which rarely survives fossilization.
The marine monster dominated the oceans between 3.6 and 23 million years ago. However, its sudden extinction has been puzzling evolutionary experts for decades. Megalodon was already over six feet long at birth, dwarfing most humans. Offspring would have been particularly vulnerable to starvation.
Zinc in tooth enameloid – the highly mineralized portion – revealed the degree of animal matter consumption. Results were as reliable as more established nitrogen examination of collagen – the organic tissue in dentine.
“On the timescales we investigate, collagen is not preserved, and traditional nitrogen isotope analysis is therefore not possible,” explains lead author Dr. Jeremy McCormack of Goethe-University Frankfurt.
Megalodon translates as “large tooth.” Researchers describe them as the “ultimate cutting tools,” broad and triangular and as big as a man’s hand. The behemoth needed to eat a lot of big prey to survive, including whales, large fish, and probably other sharks.
“Here, we demonstrate, for the first time, that diet-related zinc isotope signatures are preserved in the highly mineralized enameloid crown of fossil shark teeth,” adds co-author Prof. Thomas Tütken of Johannes Gutenberg University.
Most sharks appear to have the same diets
The study, published in Nature Communications, compared zinc levels in numerous extinct shark species from megalodon’s era with those of modern counterparts. They also looked at ratios in the giant shark’s teeth and its ancestors as well as today’s great white to shed light on their impact on past ecosystems and each other.
“We noticed a coherence of zinc isotope signals in fossil and modern analogue taxa, which boosts our confidence in the method and suggests that there may be minimal differences in zinc isotope values at the base of marine food webs, a confounding factor for nitrogen isotope studies,” says co-author Prof. Sora Kim from the University of California-Merced.
Previous studies have suggested that the megalodon could still be alive, but Prof. Shimada says that is impossible. As a warm-water species, it would not be able to survive in the cold waters of the deep – the only chance of such a creature going unnoticed.
“While additional research is needed, our results appear to support the possibility for dietary competition of megalodon with Early Pliocene great white sharks,” Shimada adds.
New isotope methods such as zinc are promising tools to investigate diet, ecology, and evolution in other fossil marine vertebrates — providing a unique window into the past.
“Our research illustrates the feasibility of using zinc isotopes to investigate the diet and trophic ecology of extinct animals over millions of years, a method that can also be applied to other groups of fossil animals including our own ancestors,” Dr. McCormack concludes.
South West News Service writer Mark Waghorn contributed to this report.